.TH std::sub_sat 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::sub_sat \- std::sub_sat

.SH Synopsis
   Defined in header <numeric>
   template< class T >                        (since C++26)
   constexpr T sub_sat( T x, T y ) noexcept;

   Computes the saturating subtraction x - y. This operation (unlike built-in
   arithmetic operations on integers) behaves as-if it is a mathematical operation with
   an infinite range. Let q denote the result of such operation. Returns:

     * q, if q is representable as a value of type T. Otherwise,
     * the largest or smallest value of type T, whichever is closer to the q.

   This overload participates in overload resolution only if T is an integer type, that
   is: signed char, short, int, long, long long, an extended signed integer type, or an
   unsigned version of such types. In particular, T must not be (possibly cv-qualified)
   bool, char, wchar_t, char8_t, char16_t, and char32_t, as these types are not
   intended for arithmetic.

.SH Parameters

   x, y - integer values

.SH Return value

   Saturated x - y.

.SH Exceptions

   Throws no exceptions.

.SH Notes

   Unlike the built-in arithmetic operators on integers, the integral promotion does
   not apply to the x and y arguments.

   If two arguments of different type are passed, the call fails to compile, i.e. the
   behavior relative to template argument deduction is the same as for std::min or
   std::max.

   Most modern hardware architectures have efficient support for saturation arithmetic
   on SIMD vectors, including SSE2 for x86 and NEON for ARM.

         Feature-test macro         Value    Std          Feature
   __cpp_lib_saturation_arithmetic 202311L (C++26) Saturation arithmetic

.SH Possible implementation

   See libstdc++ (gcc).

.SH Example

   Can be previewed on Compiler Explorer


// Run this code

 #include <climits>
 #include <numeric>

 static_assert
 (""
     && (std::sub_sat<int>(INT_MIN + 4, 3) == INT_MIN + 1) // not saturated
     && (std::sub_sat<int>(INT_MIN + 4, 5) == INT_MIN) // saturated
     && (std::sub_sat<int>(INT_MAX - 4, -3) == INT_MAX - 1) // not saturated
     && (std::sub_sat<int>(INT_MAX - 4, -5) == INT_MAX) // saturated
     && (std::sub_sat<unsigned>(4, 3) == 1) // not saturated
     && (std::sub_sat<unsigned>(4, 5) == 0) // saturated
 );

 int main() {}

.SH See also

   add_sat       saturating addition operation on two integers
   (C++26)       \fI(function template)\fP
   mul_sat       saturating multiplication operation on two integers
   (C++26)       \fI(function template)\fP
   div_sat       saturating division operation on two integers
   (C++26)       \fI(function template)\fP
   saturate_cast returns an integer value clamped to the range of a another integer
   (C++26)       type
                 \fI(function template)\fP
   clamp         clamps a value between a pair of boundary values
   \fI(C++17)\fP       \fI(function template)\fP
   in_range      checks if an integer value is in the range of a given integer type
   (C++20)       \fI(function template)\fP
   min           returns the smallest finite value of the given type
   \fB[static]\fP      \fI(public static member function of std::numeric_limits<T>)\fP
   max           returns the largest finite value of the given type
   \fB[static]\fP      \fI(public static member function of std::numeric_limits<T>)\fP

.SH External links

   1.  A branch-free implementation of saturation arithmetic — Locklessinc.com, 2012
